Device in press-roll sections for dewatering cellulose pulp webs



u so E B6 N mm 0 m9 8 m m mm n w 5 mm u mu G CF R May 18, 1965 DEVICE IN PRESS-ROLL SECTIONS FOR DEWATERING ATTYS.

United States Patent 3,183,606 DEVICE IN PRESS-RQLL SECTIGNS ESE DEWATERING CELLULQSE PULP WEES Rune Gustafsson, Stockholm, and Sven Wellmar, Bromma, Sweden, assignors to Aktiebolaget Svensha Flaktiabriken, Stochhoim, Sweden Filed Oct. 19, 1960, Ser. No. 63,635 Claims priority, application Sweden, Get. 21, 1959, 9,804/59 2 Claims. (Cl. 34-70) The present invention relates to an arrangement in press-roll sections for dewatering cellulose and similar pulp webs and equipped with heating cylinders disposed before the last press rolls. The cylinders disposed in the press-roll section serve to heat up the wet pulp web, usually prior to the last pressing stage. Such heating will reduce the viscosity of the water, the pressing operation will be more efiicient, i.e. a larger quantity of water can be pressed out of the pulp, and a correspondingly reduced quantity will remain to be evaporated by drying. On account of the inevitable evaporation taking place from the pulp web concurrent with its heating, it is impossible to impart to the web as high temperature as would be desirable in view of the above-mentioned eifect aimed at. This is due to the fact that the evaporation, taking place at a temperature dependent on the ambient atmosphere, constitutes a limiting factor in respect of the heating of the pulp web.

According to the invention, in order to avoid this drawback and to impart to the pulp web a higher temperature, the heating cylinders are shielded from the ambient air by a cabinet or casing completely enclosing the cylinders and provided, or associated, with devices by means of which the temperature and air humidity within the casing can be maintained at suitable predetermined values.

Further features will appear from the sub-claims and from the description hereinafter in conjunction with the accompanying drawing.

By maintaining the manner indicated above a high temperature and air humidity within the casing, the evaporation may be substantially avoided and mayto the extent that a minor degree of evaporation really occurstake place at a considerably higher temperature than has been possible heretofore. Since a reduction of the water content of the pulp web by some single percent involves an approximately five-fold reduction of the amount of Water which will have to be removed at a considerably higher cost by drying in a subsequent stage, the invention will enable a most considerable saving in heat in the production of dried cellulose.

The invention will now be described more closely with reference to the accompanying drawing illustrating by way of example one embodiment of the arrangement according to the invention.

In the drawing, numeral 1 designates a pulp Web com ing from a take-off section of the mill and which, in order to be subjected to mechnaical dewatering, is advanced through a number of pairs of press rolls 2, 3 and 4. Arranged before the last pair of rolls, 4, are two heated cylinders 5 and 6 serving for heating the pulp web. Numerals 7 and 8 designate two guide rollers by which the web may be caused to engage a major portion of the periphery of said cylinders to absorb heat from the cylinders by direct contact with the same.

In accordance with the invention, the cylinders are shielded from the ambient air by a cabinet or casing 9 which completely encloses the cylinders, this casing being formed with lead-in and lead-out openings 1% and 11, respectively, for the pulp web. Numeral 12 denotes a,

- aisasss Ice Patented May 18, 1965 number of perforate tubes for blowing in steam or hot wet air, as from a subsequent dryer, selectively by the operation of a suitable valve, as shown, whereby, in the embodiment shown, the temperature and air humidity within the casing can be maintained at suitable predetermined values. These tubes may suitably be arranged so as to eject the steam or hot wet air from nozzles supplied by the tubes 12 directly on to the web when, as shown in solid lines, the web is caused to pass the nozzles instead of being led directly from the roll 8 to the outlet 11, as shown in broken lines. Instead of steam, it is possible to utilize wet air emanating from a subsequent drier. The said steam tubes, as shown, may be supplemented by heaters 13 disposed within the casing and serving for maintaining the desired temperature. Numerals 14 and 15 designate two idler rollers mounted Within the casing in laterally spaced relation to the cylinders and over which the web is extended in the form of a free course 16. Numeral 17 denotes a fan which causes the steam-and-air mixture to circulate within the casing so as to maintain a uniform condition within the whole of the space therein.

The design of the arrangement may be varied in a number of ways to suit any local conditions without departing from the idea basic of the invention.

What we claim is:

1. In a press-roll section for dewatering a web of pulp material, comprising in combination, a plurality of sets of press rolls and-a dryer arranged downstream of the last set of press rolls through which the web passes, a closed casing arranged between the last sets of press rolls ahead of the dryer and through which the web passes, web contact heating means and temperature and humidity control means within said closed casing for heating said web by direct heat application while restricting evaporation of moisture therefrom, whereby to maintain a saturated ambient atmosphere about the web in said closed 'casingat the temperature to which it is raised by said contact heating means, said contact heating means comprising a heating cylinder means around which the web passes, and said temperature and humidity control means within said casing comprising pressure spray nozzles which direct hot moist gaseous fluid into the casing to maintain a hot saturated ambient atmosphere within said casing, said pressure spray nozzles being located downstream of said heating cylinder means and'arranged to direct the hot moist gaseous fluid against the web after it has been heated by said heating cylinder means.

2. A press roll section for dewatering a web of pulp material as set forth in claim 1, further characterized in that said nozzles are arranged to eject steam onto said web, and that additional heater means is disposed within said casing.

References Cited by the Examiner UNITED STATES PATENTS 1,515,614 11/24 Pinder 34-14 2,344,686 3/44 Fanselow 34-l14 X 2,711,591 6/55 Wellmar 34-18 2,760,410 8/56 Gillis 34--155 X 2,837,830 6/58 Fry et al. 341l4 X 2,838,982 6/58 Dupasquier 3437 X 3,056,213 10/62 Kellogg 3437 X OTHER REFERENCES Paper Trade Journal, vol. 138, No. 11, Mar. 12, 1954, pages 18-20.

NORMAN YUDKOFF, Primary Examiner.

CHARLES OCONNELL, GEORGE D. MITCHELL, Examiners. 

1. IN A PRESS-ROLL SECTION FOR DEWATERING A WEB OF PULP MATERIAL, COMPRISING IN COMBINATION, A PLURALITY OF SETS OF PRESS ROLLS AND A DRYER ARRANGED DOWNSTREAM OF THE LAST SET OF PRESS ROLLS THROUGH WHICH THE WEB PASSES, A CLOSED CASING ARRANGED BETWEEN THE LAST SETS OF PRESS ROLLS AHEAD OF THE DRYER AND THROUGH WHICH THE WEB PASSES, WEB CONTACT HEATING MEANS AND TEMPERATURE AND HUMIDITY CONTROL MEANS WITHIN SAID CLOSED CASING FOR HEATING SAID WEB BY DIRECT HEAT APPLICATION WHILE RESTRICTING EVAPORATION OF MOISTURE THEREFROM, WHEREBY TO MAINTAIN A SATURATED AMBIENT ATMOPHERE ABOUT THE WEB IN SAID CLOSED CASING AT THE TEMPERATURE TO WHICH IT IS RAISED BY SAID CONTACT HEATING MEANS, SAID CONTACT HEATING MEANS COMPRISING A HEATING CYLINDER MEANS AROUND WHICH THE WEB PASSES, AND SAID TEMPERATURE AND HUMIDITY CONTROL MEANS WITHIN SAID CASING COMPRISING PRESSURE SPRAY NOZZLES WHICH DIRECT HOT MOIST GASEOUS FLUID INTO THE CASING TO MAINTAIN A HOT SATU- 